1. Field of the Invention
The present invention relates generally to a system for collection and absorption of solar energy and transfer of the resulting thermal energy to a heat transport medium for use in the heating and cooling of buildings as well as domestic hot water, and more particularly to a system of this type utilizing flat plate type solar energy collectors wherein moist air flowing therethrough absorbs solar energy which is subsequently transferred to thermal energy storage means for later utilization.
2. Prior Art
Various solar energy systems and sub-systems presently available generally fall into two broad categories, i.e., active systems and passive systems. The active systems heretofore known utilize either air or a liquid, such as water, as the collector coolant and heat transfer fluid.
Such air systems generally utilize flat plate type solar energy collectors mounted on the roofs or walls of a building and may or may not use storage means such as a massive bed of rocks or pebbles, or eutectic salts in sealed containers occupying much less space but which have been found to have certain limitations and drawbacks. Some of such air systems have been designed and built utilizing hot building cavities, such as attics and walls, instead of flat plate collectors, but these are more inefficient than the ones utilizing collectors.
Such liquid systems, usually utilizing water or a water/glycol mixture, have included flat plate or concentrating solar energy type collectors. Energy storage, if used, has usually included the provision of a sealed and insulated tank, unless the system is designed for draindown, in which case the tank provided is vented and at atmospheric pressure.
None of the systems known to applicants utilize moist air as the heat transfer fluid or the principal of evaporation and condensation (phase change) to enhance heat transfer and reduce mass flow rate.
Certain disadvantages of prior art systems mentioned hereinbefore eliminated or obviated by the present include high initial cost; low efficiencies for heat collection and heat transfer; bulky heat storage devices; the necessity of providing low temperature freeze protection such as drain down or antifreeze; the necessity of providing high temperature protection means such as heat dump coils and fans; the provision of overpressure or underpressure protection means such as expansion tanks, relief valves and vacuum breakers; seperate equipment for heat dissipatation, such as cooling towers, wells, city water or air cooled refrigerant condensers; the use of fluids that cannot be mixed and which depend upon intervening heat transfer devices such as shell and tube heat exchangers submerged coils, and finned tube devices, all of which require a thermal potential (.DELTA.T) and thus a higher temperature source to accomplish the desired result; multiple fans and pumps with their attendant high first cost and maintenance cost; complex and expensive control systems; the inability to provide both heating and cooling from a solar energy source; and lack of flexibility in being adaptable to either residential or commercial buildings and to either new construction or retrofit projects.